Is an ordinary grand piano keyboard supposed to be level or tilted from front to back?

Thanks in advance for your input.

You mean the tops of the keys? If its old, there might be worn cloth under the back end of the keys causing the front end to go high. That height is cruicial to responsive touch, so you might want to get that looked at...

R Barber, thanks for the info. It sounds as though the key tops ought to be level front to back. Right?

Not necessarily. I think most keys are lower towards the back, but it is difficult to tell, as there are not necessarily good reference points. It is not the way the height of the keys is set.

Draw arc through the capstan with the balance rail hole as the center. Notice that the capstan wipen point is farther along the circle when the key is flat and the capstan now is moving forwards and backwards instead of just lifting straight up or in the line of the arc of the wippen. This causes a scrubing on the pad and increases friction and wear and directs energy in useless directions.

It's all about Jack, as Randy Potter would say.
The key height would determine the alignment of the jack to the knuckle core, and when the keyboard cloths get worn, the keys tilt, and the jack ain't where its supposed to be.
I have heard some artists refer to this tilt in terms of numbers, like "I like more of a 1, where as this piano is a 3" while they make the tilting gesture with their hands. When asked what it does for them, they say when the angle is correct, there is a better dynamic range.
A technician may then verify the jack to knuckle core alignment before messing with the balance rail.

I'm confused by what you say. Is it not true that the wippen has to be at the same place relative to the strings when letoff occurs, irrespective of key angle? Also, isn't it true that the relationship of the jack and knuckle to the line of centers between the wippen flange and hammer flange is completely determined by the diameter of the knuckle and the relative mounting positions and dimensions of the wippen and hammer? Basically, it seems to me that these action parameters are determined by everything other than the key angle.

You are correct, Roy.

Yesterday I tuned two concert grands. One had rocker arm capstans, and the other screw capstans. That difference is not noticeable.

(For those who do not know, rocker arm capstans are fastened to the wippens by wooden stickers, so there would not be any "scrubing [sic] on the pad" in any circumstances.

Yes it's normal for the keys to be tilted from front to back.



Typically about 1/4" from the front edge of the key to the fall
board.



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What I am saying is apparant on the diagram above: there is a cloth under the back of that key- check to see if it is worn out. It's thickness will affect the tilt and the position of the top of the jack with respect to the knuckle core while at rest on the key cloth. If the cloth is worn, you might try that capstan adjustment, but you will waste your time because you will do 88 of those, and fidget with other things, but will not have resolved the fact that there may be worn felt under there, which might have 2 or 3 or more mm of indentation, causing the keyboard to tilt by an even greater amount at the fronts. This would mean excessive dip, which would mean a change in the aftertouch (and where the whippen moves after letoff).
It made so much more sense in Randy's class at the convention.